A light measuring device of the type mentioned above is disclosed, for example, in U.S. Pat. No. 5,115,126. In the case of this light measuring device, which is used for testing endoscopes, the light emitted from a light source is fed via a light guiding device to a sensor arrangement, the endoscope there being tested by comparing the output signal of sensors.
It has already been proposed once to implement a sensor that has a smaller diameter than the light guide and its light exit surface. This solution attempts to enable measurement of the output illumination intensity independently of the diameter of the light exit surface. However, with this solution there is the grave disadvantage that fundamentally only the luminous density in the measured region of the light exit surface is detected. This means that only a lesser fraction in percentage terms of the emitted light power is detected in conjunction with a comparatively large light exit surface, and so erroneous measurements occur to this extent on different sizes of the light exit surfaces.
In particular, even in the case of this solution it is not possible to conduct a distance measurement in which the light curing device is thus merely held over the sensor field in order to determine whether the emitted illumination intensity is still sufficient, because erroneous measurements then always occur in the case of this solution owing to the beam expansion.
In accordance with published patent application US 2008-0023625-A1, it has been proposed to use a one-dimensional arrangement of light sensors, and their output signal in order to determine the light power of a light source. This solution is simple in principle and constitutes an improvement against the previously known solutions. On the other hand, this design is not able to deliver an exact measurement result when the light exit surface has a shape deviating from the circular one.
By contrast, it is the object of the invention to provide a light measuring device that enables a reliable and simple determination of the illumination intensity independently of the shape of a light exit surface.